1. Field of the Invention
The present invention relates generally to a transport assembly or conveyor, and more particularly, to a method for identifying the position and size of an object on the transport assembly.
2. Description of Related Art
In order for a controller of a transport assembly to compute the position of objects positioned thereon, the controller continuously receives sensory information that identifies the presence or absence of an object on sensors embedded in the transport assembly. After receiving the sensory information and computing a position of the object on the transport assembly, the controller corrects discrepancies in the desired position, orientation, and speed of the object by outputting commands to actuators in the transport assembly.
To reduce fabrication costs and insure scalability of the transport assembly, the number of sensors and the amount of information provided by the sensors needs to be minimized. Accordingly, it is desirable to minimize the amount of sensory information necessary to precisely and rapidly control in realtime the position and velocity of an object moving on the transport assembly. In addition, it would be advantageous if the controller were sufficiently robust to accurately determine the position of the object on the transport assembly in the presence of noisy sensory information.
In accordance with the invention, there is provided a transport assembly for moving objects thereon. The transport assembly includes a transport controller that computes a position of an object on the transport assembly from sensor output. In accordance with one aspect of the invention, the sensors are arranged on the transport assembly in a pattern that is adapted to produce boundary information of objects positioned thereon. In one embodiment, the sensors are arrays of point sensors that are arranged perpendicular to each other. In operation, each sensor array outputs one or more boundary points when an object covers only part of the sensor array.
In accordance with another aspect of the invention, the transport controller computes an equation of a rectangle that minimizes the deviation of boundary points, output from the sensor arrays, from the boundary of the computed equation of the rectangle. From the computed equation of the rectangle, the position of the object on the transport assembly is determined. Advantageously, the transport controller computes the equation of the rectangle even though boundary points are received from the transport assembly in the presence of noise (i.e., the points do not lie precisely on the boundary of the object on the transport assembly). After determining the position of the object on the transport assembly, the transport controller adjusts the actuators to direct the object to its desired position.